1. Field of the Invention
The present invention relates to electric centrifugal fans.
2. Description of the Related Art
Hybrid cars and electric cars, which utilize a driving force developed by motors for vehicle propulsive power, have gained more and more attention in recent years. These vehicles are typically equipped with rechargeable batteries which store electric energy to be used for driving the motors. Since the batteries, however, have internal resistance, heat is generated when power is charged or discharged. The repeated charging/discharging causes the temperature to rise in the batteries. Continued use of the batteries during high temperature conditions causes a shortening of the life of the batteries, and the batteries therefore require cooling. In order to cool the batteries, centrifugal fans have conventionally been used.
For installing a centrifugal fan in a vehicle, it is desirable to design the space for disposing the batteries and the centrifugal fan for cooling the batteries to have the smallest possible size so that a large cabin space and cargo space can be achieved.
Regarding conventional centrifugal fans, there is known a structure in which, e.g., high heat generating power devices (electronic components containing a control circuit of the motor) are attached to a surface that is opposite to the surface in which the intake port of the casing is provided. With this structure, heat generated in the power devices can effectively be dissipated to the casing.
With the conventional structure, however, the centrifugal fan has a considerable size. When such a conventional centrifugal fan is installed in a vehicle, it becomes difficult to achieve a large cabin space and cargo space.
This kind of problem is not unique to the cooling fans for the batteries mounted in vehicles, but may occur in other apparatuses with centrifugal fans for cooling heat-generating parts, such as electronic devices that are required to have a minimal size and thus there is limited installation space for the centrifugal fans.